The present invention relates to a sheet feeding mechanism in use with an ink jet printer, for example, and more particularly to a sheet feeding mechanism including an object pressing member for pressing a printed sheet.
To print by an ink jet printer, the nozzle orifices of a printhead selectively eject ink drops onto a printing paper in accordance with print information while synchronizing with a relative movement of a printhead relative to a printing paper.
Generally, to feed a printing paper in the printer, the printing paper is nipped by a pair of paper-feed rollers, and one of the paired rollers is rotated.
In the case of the ink jet printer, characters, for example, printed on the printing paper are not fixed. Accordingly, when the printed paper is pressed against the rollers, ink of the printed characters is still wet. The wet ink sticks onto the roller, and is transferred from the roller to the sheet or paper.
An ink jet printer designed to solve the ink sticking problem is disclosed in JP-A-2-41277.
In the ink jet printer, the sheet is held by pressing the medium on the sheet feed roller. Therefore, the ink jet printer indispensably includes a sheet-pressing member having a spur gear with sharp teeth on the shaft.
The sheet-pressing member is designed to act elastically to the spur gear or the shaft, and the thus designed member presses the printing paper against the sheet feed roller.
A contact area where the spur gear is in contact with the paper is small in the ink jet printer using the thus constructed sheet-pressing member. Therefore, no ink transfer to the paper takes place in such a printer.
The sheet-pressing member of the printer takes the form of a bar or a plate, and the thus shaped member, while being bent, presses the sheet against the sheet feed roller.
The sheet-pressing member has a large spring constant, and inevitably suffers from dimensional variations. For this reason, work to properly set a pressing force is very difficult.
Where the pressing force is too large, an excessive load acts on the paper being fed. On the other hand, where it is too small, a sheet feeding force is insufficient. Either case leads to degradation of print quality.